What is the greatest common factor of $10$ and $45$ ? Another way to say this is: $\operatorname{gcf}(10, 45) = {?}$
The greatest common factor is the largest number that is a factor of both $10$ and $45$ The factors of $10$ are $1$ $2$ $5$ , and $10$ The factors of $45$ are $1$ $3$ $5$ $9$ $15$ , and $45$ Thus, the greatest common factor of $10$ and $45$ is $5$. $\operatorname{gcf}(10, 45) = 5$